Patent GB-743672-A (GB)
Title: Improvements in or relating to display apparatus
IPC: G11B33/06
Filed: 1953-03-31
Abstract: 743,672. Magnetic recording and reproducing apparatus. FRANCO-BRITISH ELECTRICAL CO., Ltd., and BRACKENSEY, A. H. March 30, 1954 [March 31, 1953; Oct. 2, 1953], Nos.. 8965/53 and 27128/53. Class 40(2) [Also in Group XVIII] A display installation (see Group XVIII) comprises a tape recorder 1, Fig. 1, at least one model H, a dubbing unit 27, a power unit 45 and a decoding unit 53. The tape recorder is provided with two record/reproducing heads 9, 19, each of which embodies eraser means. The. head 19 is adapted to impart an " action " track for the model on the tape after the sound track is added. thereto. The action track is added by the dubbing unit 27, see also Fig. 3, which is arranged to be keyed manually or automatically as required according to the setting of push. buttons 35, 36 respectively. The units 1. 27 are interconnected when the ganged switch arms of switches 37-39 and 41-43 are moved to the left. The power unit 45 comprises a D.C./A.C. power pact 54 arranged to give various outputs and a multi-stage electronic audiofrequency amplifier 47 which is connected to the decoding unit 53 having five output relays 60-64. The dubbing unit. Fig. 3. comprises a transformer 70 having a secondary winding 71 connected to a selenium rectifier 79 producing high tension D C. and a secondary winding 72 which serves for the energization of a warning light 73 and also for the heater windings of the valves 74, 75. 76. When one of the push buttons 29-33 is depressed it brings a condenser such as 85 into parallel with a coil 88 so that the valve 76 which constitutes a transitron pentode oscillator will oscillate at the desired frequency. A condenser 76A is provided to stimulate oscillation of the valve 76 and the voltage is stabilized by a gasfilled diode stabilizer 76B. A substantially constant amplitude output from the oscillator is maintained by a condenser 105. The unit also comprises switches 108, 109 which are controlled by the buttons 35, 34 respectively; the button 34 acting as a morse tapper key. When the button 35 is depressed it will cause the button 36 to lift and vice-versa. The button 36 controls ganged switches 110, 111; the switch 111 being connected to the primary winding 112 of a transformer having a secondary winding 113 which is connected to a rectifier bridge 114. The rectifier 114 is also connected with a solenoid winding 115 having a core 116 which is adapted, when the solenoid is energized, to open the normally closed switch contacts of the arms 117 and 118. The series arranged switches 110, 117, 118 are in parallel with the switches 108, 109 and the switch 111 is connected to the input lead 42A which brings audio-frequency signals from the unit 1 when-it is reproducing. The triode 75 is arranged as an R/C amplifier whilst the valve 74 is an output pentode connected to act as an oscillator, the frequency of oscillation being determined by an inductance 134 and a condenser 136. The arrangement is such that the dubbing unit develops from the oscillator 76 signals where frequency is chosen by depressing one: of.. the buttons 29-33; the output being maintained at constant amplitude and applied to the amplifying valve 75 so that an amplified signal of selected frequency is fed therefrom. The decoding unit 53, see Fig. 4, comprises a high gain pentode amplifier valve 202 which operates on the principle of grid leak bias amplification. The output is fed to the first control grid 220 of a double triode 221, 221A having a second control, grid 222. The double triode is connected, as a two stage R/C amplifier as shown. The amplified output is fed in parallel to the first control grid of each of five further double triodes such as. 225, 225A. The. anode 228 of the triode 225 is joined to the grid 230 of the triode 225A through a coupling condenser 231 and a resistor 232. The grid 230 is also joined to a parallel resonant circuit formed by a condenser 233 and an inductance 234, connected to the earth 208. The parallel circuit is resonant at a particular frequency equal to the frequency of the action signal produced by the unit 27 when. a particular button is depressed. A signal can be fed to the lead 58 having one of five frequencies so that one of the five double triodes 225, 225A will respond: The anode 242 of the triode 225A is transformer coupled to a selenium rectifier bridge network 243. The input 57A of the decoding unit is joined by a lead 245 to each of the relay units, see also Fig. 6 (not shown), in parallel and the input terminals 52, 52A are respectively connected to. movable and fixed contacts 246, 247 which normally abut one another to prevent open-circuiting of the output from the amplifier 47 of the power unit 45. The contact 246 is moved under the influence of a winding 250, one end of which is parallel connected to each of the relay units 60-64 whilst the other end is connected to one D.C. junction of a rectifier bridge network 252 having A.C. input terminals X. Y. The D.C. junctions of network 252, are also connected to each of the relay units 60-64 in parallel as is the contact 246.